Update python Docker tag to v3.10.15 (#8296)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

docker/Dockerfile

@@ -12,7 +12,7 @@ RUN yarn build
 
 
 ## Backend stage
-FROM python:3.10.13-slim-bullseye
+FROM python:3.10.15-slim-bullseye
 
 WORKDIR /app
 

docker/dev.Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.10.13-bullseye
+FROM python:3.10.15-bullseye
 
 # Variables that are not specific to a particular environment.
 ENV NEW_RELIC_CONFIG_FILE newrelic.ini